Laissez-faire lumping under fire? (babirusas, part VII)

In the previous article we looked at the proposal that the various babirusa taxa - long regarded as subspecies - deserve to be raised to species rank. The argument goes that the taxa concerned are (1) morphologically diagnosable, (2) 'as distinct' as are other taxa traditionally regarded as species (raising the taxa to species level therefore represents a sort of attempt at uniformitarianism), and (3) represent distinct phylogenetic lineages. Meijaard & Groves's proposal therefore reflects their adherance to the phylogenetic species concept, or PSC (where distinct lineages on a cladogram have to be regarded as distinct taxa), and should not be regarded as mere subjective 'splitting'. Predictably, any suggestion that a traditional 'species' - like Babyrousa babyrussa - should be split into several or many has resulting in some criticism (see the Tet Zoo comments here and here).

Are criticisms like this justifiable? We begin with the observation that the division of a traditional 'species' (like Babyrousa babyrussa) into several 'phylogenetic species' reverses the trend of the early 20th century: at this time, multiple large mammal species previously erected by Victorian (and earlier) naturalists were lumped together.

It now seems that at least some of this lumping was over-zealous and in fact rather lazy, and it's for this reason that I refer to it as laissez-faire lumping. This opinion is not my own: I have been inspired by such mammalogists as Colin Groves, Peter Grubb, Jeheskel Shoshani and Esteban Sarmiento. In arguing that the two African elephant species Loxodonta africana and L. cyclotis should be separated as distinct species, Grubb et al. (2000) wrote...

'Biodiversity of large mammals is severely underestimated. The existence of a narrow hybrid zone among large mammals can be detected in casual field surveys, which is not the case for small mammals and other animals that have to be trapped for close investigation. This simple fact has led to the downgrading of perfectly distinct, diagnosable species to a level where they become taxonomically 'invisible' and thus lost to biodiversity studies. There are many examples of large mammal genera in which single species are currently supposed to extend through forest and savannah zones (as in the elephant case treated here), and this series of case studies might be a place to start testing the proposition that their biodiversity has been underestimated' (p. 3).

While biologists tend to be harshly critical of workers who erect new taxa based on only small apparent differences (such workers become known as 'splitters'), there is far less criticism of those who indulge in laissez-faire lumping: it's almost as if the lumpers are regarded as the ones with the most realistic handle on species-level biodiversity. But are they? Well, as African elephants and the various other examples cited above seem to indicate, perhaps they aren't in all cases. Indeed, we should be as sceptical of lumping as we are of splitting. Such things as the several proposed babirusa species, the different warthogs, and the gorilla and African buffalo species are all morphologically distinct, and arguably 'as distinct', or 'more distinct', as are long-recognised species accepted without question in other groups (I'm looking at such passerines as Dendroica and Empidonax... shudder).

Kill subspecies, kill species... time to move on?

One reason that a lot of people dislike 'phylogenetic species' is that such entities often differ from the species recognised by tradition. But this is because 'phylogenetic species' and 'traditional species' are not really the same thing: 'phylogenetic species' are (so far as I understand from the writings of Joel Cracraft and others) meant to respond to irreducible clusters of individuals: that is, to the smallest distinct subdivision of a given taxon. The conventional idea of a species is actually something rather vaguer: it usually encapsulates some subjective notion of similarity (e.g., population A and B belong to the same species because they're 'similar enough' and can probably interbreed).

Perhaps the tidiest solution is simply to do away with the notion of species and subspecies entirely and work with something else, such as the 'least inclusive taxonomic units' of Pleijel & Rouse (2000). Sluys & Hazevoet (1999) argued that we should be naming diagnosable phylogenetic entities, and that traditional concepts of 'species' and 'subspecies' were misleading and carried too much historical baggage to be reliable.

One problem with all of this is that - for some of the taxa concerned (I'm bringing it back to babirusas now) - all too little work has been done on phylogenetic structure and so on. The proposal that 'Babyrousa babyrussa' of traditional includes several, morphologically distinct lineages that deserve to be recognised as 'species' is based on the morphological differences observed between these respective populations. The idea that these warrant recognition as distinct taxonomic entities may well be valid, but it's a hypothesis and we need more information before we can be confident that we're not being confused by something else, like the sort of ecomorphological plasticity present in some species (like Lions Panthera leo). However, remember that we discover more by assuming less: many of us make conclusions about megamammal taxonomy based on assumptions (e.g., that more than one living elephant species in Africa is too many*), not on the data that now bears on the issue.

* I never understand arguments like this, given that the modern world is horribly impoverished compared to the situation of just a few hundred thousand years ago.

Finally, what's with the photos used at the top?, I hear you cry. Both photos are of the Golden babirusa or Hairy babirusa B. babyrussa specimen on display at the Raffles Museum of Biodiversity Research (photos kindly provided by Ivan of The Lazy Lizard's Tales). It was killed on Buru and donated to the museum in 1913 by G. P. Stubbs. Virtually all other photos out there are of the more naked-skinned B. celebensis, so I was very excited to see these pictures. The animal's blonde pelt is particularly striking (though note that I've tinkered with the contrast a bit).

Xu, X. & Arnason, U. 1996. The mitochondrial DNA molecule of Sumatran orangutan and a molecular proposal for two (Bornean and Sumatran) species of orangutan. Journal of Molecular Evolution 43, 431-437.

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Welcome to yet another article in the (outstandingly successful, yet recycled from ver 1) series on babirusas. Observant readers will have noticed that, strangely, I've refrained thus far from using a scientific binomial for babirusas, plus I've consistently (I think) referred to them in the…

I covered babirusas recently; you might have noticed. As you'll know if you read those articles, Meijaard & Groves (2002a, b) argued a few years ago that Babyrousa babyrussa of tradition should actually be split up into several phylogenetic species. Coincidentally, I published an article on…

If you're a regular reader you'll have seen the recent article on those African 'great bubalus' depictions and on how they might (or might not) be representations of the large, long-horned bovin bovid Syncerus antiquus. As discussed in that article, S. antiquus - long thought to be a species of…

One of the most remarkable pigs has to be the Bornean bearded pig Sus barbatus, one of two currently recognised bearded pig species. The other is the much smaller, shorter-faced Palawan bearded pig S. ahoenobarbus of the Philippines: genetic work suggests that S. ahoenobarbus is not a close…

I am as an opponent of lassaiz-faire lumping as I am of overanalytical splitting. Both attempt to resolve the problem of arbitrary nomenclature by focusing on two different aspects of the same system:

1. Lumpers reject (in general) the principle that novelties among species are important, or special, outside the general evolutionary flow. That is, they see new features as being simply unique to a population, and will reject attempts to fission off elements of this system as being phylogenetically important.

2. Splitters reject (in general) the idea that variation isn't a holistic method of evaluating evolutionary diversity. That, instead, they view variation or value of unique qualities, to be worthy of recognition as element son which the evolutionary framework can expound upon.

Both groups reject the conservative option, that of figuring out whether features in any system have value, or that different features in the system with have different values in a population. Or even that population-level genomics can say anything about "species" level genomics, and that opens a new door of where lumpers and splitters divide: The value of taxonomy to the system. And we're not even talking about how the conservation and preservation of genetic lineages in zoos or wilderness areas influences the politics of species recognition, promoting lumping over splitting.

I think that different species concepts name different kinds of entities; many of those kinds are actually interesting, and therefore should be named (so we can talk about them), but they overlap â rank-based nomenclature can't deal with that, and phylogenetic nomenclature can only name taxa that can be defined phylogenetically, which is not possible for every species concept. We're going to need several parallel nomenclatures...

images at left: how many species do you see?

What. Are both of them supposed to be Syncerus caffer? Under what, if any, species concept...?

(Yeah, OK. They can most likely interbreed, and in that case they're the same species under at least one of the Biological Species Concepts.)

Yeah, I was being a prat, but I do have a point. We have to call our units-of-organisms something and as the term 'species' is already deeply entrenched among both scientists and laypeople, is not the most parsimonious solution to keep using it? That the term 'species' carries lots of historical baggage may be (at least to some extent) true, but it's almost certainly much, much too late to do anything about that. For better or for worse, I'd say that we are stuck* with 'species'.

Unless I totally misunderstood what Darren wrote in the original post, those references he cited were advocating the wholesale abolishment of the term 'species' - a proposal that I really can't see the benefits of. If anyone is unnecessarily chopping off taxonomic units here, it would seem to be Pleijel & Rouse (2000) and Sluys & Hazevoet (1999), respectively. (Though I should add the disclaimer that I haven't yet looked up either source myself to see what they specifically say.)

"Indeed, we should be as sceptical of lumping as we are of splitting. "

I may be wrong, but...
Isn't there a bigger ego pay-off for the splitter? A splitter gets to name "new" species, and be forever after referenced (or at least long as his species concept survives). Thus it's easy to understand why people might err on the side of splitting. Is there a comparative selfish benefit to lumping?

Be careful. Discussions of species concepts can become both contentious and interminable. But it seems to me that the current difficulties are less to do with species concept than with lack of data to apply to any concept, and secondarily with the fuzziness around the edges of both the major current concepts (BSC and PSC). There are also several variant versions of the PSC, to increase confusion.

So, do any of the babirusa "subspecies" exchange genes? Or, if they're allopatric, would they if sympatric? Are they all reliably diagnosable? If now allopatric, have they been so for long enough to become reciprocally monophyletic at most loci? And so on.

When we revised the Rivulid killifish genus Austrofundulus in 1978, we removed one species to a new genus, elevated two subspecies to full species,and lumped two previously described species with one of the newly elevated species, A. limnaeus. We recognized various distinct allopatric populations in A. limnaeus, but did not recognize them as subspecies.

In 2005, armed with DNA data, we revised Austrofundulus once again. and recognized seven species. All of the previous distinct allopatric populations except one were removed from A. limnaeus. A limnaeus is distributed along the east coast of Lake Maracaibo, with the type locality out in the coastal desert. It turns out that there is a continuous distribution down the coast (which we did not know in 1978) and a broad intergrade area, both morphological and DNA wise between the two quite morphologically different end populations. The end populations are similar enough in DNA that we were comfortable retaining them in a single species.

It amuses me how different the various species look to me now that I know they are separate species.

So far as lumping or splitting goes, you become an immortal either way, so long as the International Code of Zoological Nomenclature survives the ongoing decay of Western civilization.

The end populations are similar enough in DNA that we were comfortable retaining them in a single species.

Was there a specific numerical threshold of similarity that these populations met?

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Fuzzy Babs. Nice!

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Following on one of David's points:
The species vs. subspecies dichotomy is itself a sort of artificial splitting. In nature it is, of course, a smooth continuum. One could informally add other categories such as:
1. Incipient species
2. Species-to-be
3. Species-in-waiting
4. Wannabe species
5. Coulda been species
etc.

Well, now there is one dominant species concept: one which-author-thinks-can-make-most-fuss species.

Interestingly, IUCN red list lists again the one and only red deer. And lumped forest elephant back into Loxodonta africana. With the explanation: "The African Elephant Specialist Group believes that more extensive research is required to support the proposed re-classification. Premature allocation into more than one species may leave hybrids in an uncertain conservation status."http://www.iucnredlist.org/apps/redlist/details/12392/0

What a wonderful, open admission that species concept is tweaked to suit conservation strategies. But it makes sense - when hybrid zones or intermediate populations are significant percent of the total, how you name research on them?

I finally saw the BBC production of Terry Pratchett's "Hogfather" (recommended -- and with excellent casting, BTW, and available from Netflix) which featured prominently, to my amazement, four babirusas pulling a sleigh. Unfortunate as it may have been, they could not muster live babirusas for the role, although the actors must have appreciated the omission.

Incidentally, my kids (8 and 10) finally got to see the National Geographic series "Inside Nature's Giants", on Youtube, and were enraptured. I was too.

I suppose paleontologists usualy deal with limited samples, so are completely unaware about variation and intermediates within species.

The reason why large mammals are lumped is that people who work in the field are aware of hybrid zones and intermediate populations. So forest and savanna buffalos which look strikingly different are connected by many intermediates and regional variations. So, no 2 species - either 1 or 10 or 20 buffalo species.

Now the problem is made worse, because DNA sampling is naturally made on limited samples - producing artifical sharp clades, and populations become fragmented - artificaly removing intermediates.

Yes, John, the Babirusa is kosher, and it is halal as well. I quote no less an authority than Patrick O'Brien, in The Thirteen Gun Salute:
"...this animal was almost certainly a babirussa of nine or ten score, the first he had seen since Thursday week. He was glad of it, because the ship's company included several Jews and many Mahometans, united only in their hatred of swine's flesh, but a willing mind could accept the babirussa, with his extraordinary horn-like upper pair of tusks and his long legs, as the kind of deer that might be expected on so remote an island."

Did you somehow manage to miss the recent 'Death of Tetrapod Zoology' post? Darren has made it quite clear that he is currently unable (for both professional and personal reasons) to produce substantial amounts of new material for his blog. His options are to recycle old posts, or to post nothing at all. Personally, I vastly prefer the former to the latter. If you don't like either option, there are other science blogs out there.

Jerzy:

Now the problem is made worse, because DNA sampling is naturally made on limited samples - producing artifical sharp clades, and populations become fragmented - artificaly removing intermediates.

In the comments thread of the previous post, you were unhappy with Groves' and Meijaard's morphology-based revisions of babirusa taxonomy. Now you are complaining about DNA data. So what methods do you suggest we should use in taxonomy, then?

And please, let's have less (or better still, none) of the borderline offensive 'only people who work in the field know what species really are' stuff. 'People who work in the lab' contribute just as much, and arguably more, to taxonomy.

I thought Jerzy made pretty clear that what he wants is many more, and more widely collected, samples of each taxon, and for lab people to get out more so they can get an idea of what kind of variation is really there. Neither suggestion seems objectionable, except perhaps to the specimens sampled.

"The African Elephant Specialist Group believes that more extensive research is required to support the proposed re-classification. [...]"

The same research, however, is also required to support the current classification. There isn't some sort of default there.

I suppose paleontologists usualy deal with limited samples, so are completely unaware about variation and intermediates within species.

There are fossil species (especially, but by no means only, if you look beyond the vertebrates) that are known from hundreds or thousands or millions of specimens. Witness the extreme splitting of Triceratops (16 species or so) in the 19th century, the complete lumping into one species in the 1990s, the resplitting into three (including Diceratops, a preoccupied name recently replaced by Nedoceratops) which went back and forth several times, and the ongoing lumping of Torosaurus into Triceratops as its adult stage...

In species, you often have relatively uniform subpopulations and large clinal variation across broader geographic range. Plus lots of local forms often linked to local topography. If you pick only a few distant populations (by morphology or DNA sampling or paleontological record) you often find big differences. To say if they are different species you need to check intermediate populations - do you have clinal variation or broad hybrid zones, or a zone of sympatric overlap. Both BSC and PSC are here the same.

Here is example of brown bear, where first scientists found significant genetic differences. Later more extensive sampling revealed that sometimes lineages occur together, and in some cases geographicaly separate lineages today, which were earlier picked as of conservation importance, co-occured in one population in the Pleistocene.

One mistake frequent today (eg. giraffe) is to study currently separate sub-populations without thinking that historically they were linked (either 100 years ago before large-scale hunting, or 10,000 years ago when sea level was lower in Pleistocene).

I would say that anything which is parapatric and not as different as related sympatric species are between themselves should be lumped, unless you have clear evidence that hybrids have reduced fertility.

In case of babirusa, they are different, but so are common wild boars Sus scrofa from Siberia and S Asia.

Regardless of how they might be split out at the genus/species level, are they not lumped together with other pigs under the higher taxon Suidae? If all Suids are pig variants, then all of them are neither kosher nor halal anyway, given that the flesh of pigs is explicitly forbidden in the Torah and Quran.

Of course, I suppose it might be argued that a pig that actually did chew cud is sufficiently distinct from all non-cud-chewing pigs to not be called a pig anymore for the purpose of kosher/halal, but that way, I suspect, lies madness, and also bacon (if the rabbis and imams go mad, they might well eat whatever they want anyway).

I would say that anything which is parapatric and not as different as related sympatric species are between themselves should be lumped

But what metric would you use to decide how different is 'different'? Molecules? Morphology? A combination of molecules and morphology? Something else?

In case of babirusa, they are different, but so are common wild boars Sus scrofa from Siberia and S Asia.

Yes, and over the years there have been plenty of studies that have suggested splitting Sus scrofa sensu lato into several distinct species. That particular taxonomic mess dwarfs the babirusa case anytime.

Owlmirror:

If all Suids are pig variants, then all of them are neither kosher nor halal anyway, given that the flesh of pigs is explicitly forbidden in the Torah and Quran.

If babirusas might be considered kosher/halal (at least by some), then what about peccaries?

So now we have claims on both sides of the kosher/trayf pig controversy. What we lack is data. Babirusa are kosher if and only if a some rabbinical authority has so designated them. (If there are rabbinical opinions on both sides, you pick your authority.) So who has actual information on this, if anyone?

Same point applies for halal/haram.

While there are many claims on the web (including the wikipedia article) few of them have references to any authority. This is the best I could find so far:

The list of animals forbidden by kashrut is more restrictive, as kashrut requires that, to be kosher, mammals must chew cud as well as have cloven hooves. DhabiÄ¥a halal only requires that an animal survive on grass and leaves.

Babirusa and peccaries are non-ruminant omnivores.

Even if some member of the Suini/Suidae were found to be a (vegetarian) cud-chewer, I suspect that rabbis and imams are naturally conservative lumpers, and that therefore they would find the explicit prohibition on pig to be binding. Convince them to be splitters, such that only members of Sus (or whatever) that are non-ruminant omnivores are considered pigs under the rules of kashrut/halal, and you're done.

(And shortly thereafter, there will also be Babirusa that proudly spread their wings and fly to the moon.)

On kosher/trayf, it seems to me that someone would at some point have asked for a ruling. Does anyone know of any?

On halal/haram, does anyone know of a ruling?

Because you can say, for perfectly rational reasons (well, not rational, but at least logical and consistent) that babirusa should not be kosher or should/should not be halal, but what actually counts is what the religious authorities say. And that's the question. Are there any such opinions?

Because you can say, for perfectly rational reasons (well, not rational, but at least logical and consistent) that babirusa should not be kosher or should/should not be halal, but what actually counts is what the religious authorities say.

I think it's a reasonable inference that a religious authority is not going to contradict a long-held tradition based on an explicit law.

Again coming to the definitive conclusion that the babirusa was never ruled as kosher, and based on Jewish law as currently understood by all authoritative orthodox rabbis, will never be ruled as such. Note that it also addresses peccaries (tai'asu or tayassu) on pg 76-77.

I note that The Thirteen Gun Salute was published in 1989 -- perhaps Patrick O'Brian saw the (incorrect) Associated Press report from 1984 referenced in the texts I've linked to, and inserted the paragraph @#19 based on that.

It looks like that kashrut status of a putative cud-chewing Suiforme is less certain than I thought -- there appears to be arguments both for and against it being considered kosher. Oh, well.

Also: A more detailed discussion of the kashrut of the babirusa is here:

â Contemporary Halakhic Problems, by J. David Bleich, pp 66-77

Why, thanks. Exactly what I was asking for, and fascinating reading if you go for that sort of thing. I note that on page 72 there is iron-clad proof that cows are not kosher, if you accept the theory that ruminants evolved from non-ruminants. (A kosher animal is the offspring of a kosher mother, and a mutation that, for example, turns a non-ruminant into a ruminant, does not succeed in making the animal kosher. The distinction apparently runs back to the creation. Take away the separate creation of kinds, and the system crashes.)

One thing about this continuous debate over taxonomy is that definitely is good for academics. One can find a niche very easily defending the validity or attacking the validity of whether an organism is a full species or merely a subspecies.

Coming up with a hard and fast definition of the clear distinction between subspecies has an inherent pitfall: the natural history of every organism on the planet is different. In some cases, it does make sense to raise a subspecies to a full species status (like the recent separation of Bornean clouded leopard from the mainland clouded leopard species). In others it really doesn't. I'm skeptical about the move to separate the Indian wolf from C. lupus, although I'm sure some will disagree with me on that one. It certainly helps that highly endangered wolf if it is a full species, because now we can focus on it as a very endangered species, not a subspecies that will become extinct. I hear very few people crying over the loss of the Shamanu.

Drawing a hard line with taxonomy merely limits us too much. We have to have both lumping and splitting. And we have to have debate on it.

Mayr's definition of a species is a good place to start, but it's not the only thing to examine.

One supposes that not all species definitions are of equal value, although one or another may work best in a particular situation. Mayer's definition works pretty well a lot of the time. It is a good place to start thinking about what a species is. I suspect, as I type, somewhere in the world there is a learned conference being held to discuss the nature of species.

OK, so I get in my car this evening and turn on the local Seattle public radio station, and who of all people should come on but Darren Naish, talking to the BBC about the new Science paper on the K-Pg extinction! Very cool.

Congratulations, Darren, nice job on the air, and good luck with your current projects!

One supposes that not all species definitions are of equal value, although one or another may work best in a particular situation.

IMHO, many species concepts designate interesting kinds of entities -- but to pretend that those entities are all somehow the same (and can therefore all be called "species") just doesn't work. We shouldn't need to decide between them, we should be able to use them all at once, and the current methods of nomenclature don't allow that.

Mayer's definition works pretty well a lot of the time.

What do you mean by "work"?

I suspect, as I type, somewhere in the world there is a learned conference being held to discuss the nature of species.

There've been several, and each has produced a big fat book. All that really happens is that the number of species concepts keeps increasing.

Darren Naish, talking to the BBC about the new Science paper on the K-Pg extinction!

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